The present invention relates to an apparatus and a method to treat a disease process in a luminal structure. Such a structure includes, but is not limited to, a vein, artery, bypass graft prosthesis, the gastrointestinal (GI) tract, the biliary tract, the genitourinary (GU) tract, and the respiratory tract (e.g. the tracheobronchial tree).
Percutaneous transluminal coronary angioplasty (PTCA) is commonly used in the treatment of coronary artery obstruction, with over 400,000 procedures performed annually. PTCA is one of the most common current therapies for obstructive coronary artery disease (1). Unfortunately, it remains limited by a 30%-50% restenosis rate (2-5). The PTCA process involves the insertion of balloon catheters through the femoral artery to the targeted coronary artery. Injection of radio-opaque contrast into the proximal coronary artery allows fluoroscopic localization of stenosed coronary segments. Balloon catheters are advanced to the site of stenosis over extremely thin guide wires to position the catheter at the point of occlusion. The distal end of the catheter contains a balloon which is inflated for 2-4 minutes to the full diameter of the occluded artery, decreasing the blockage and improving blood flow.
In a related area, brachytherapy involves the implantation of a radioactive source within tissue to deliver localized radiation and is frequently applied to treat recurrent disease in an area previously treated by external beam radiation. Blind-end catheters may be used to deliver radiation to tumors in the esophagus, trachea, or rectum, for example. Advantages include the sparing of critical structures close to the tumor, and brevity of treatment (hours to days). Difficulties primarily involve anatomic constrains on implant placement. Common applications include the endoluminal treatment of recurrent endobronchial and bile duct tumors, the intracavitary treatment of cervical and endometrial cancer, and interstitial implants in unrespectable tumors with catheters or radioactive seeds.
As stated above, restenosis after arterial intervention in general, PTCA in particular, seem to be primarily due to medial smooth muscle cell proliferation. Conventional PTCA is performed using a balloon catheter such an over-the-wire type catheter manufactured, for example, by Scimed Life Systems, Inc, of Maple Grove, Minnesota or a mono-rail type catheter manufactured, for example, by Advanced Cardiovascular Systems, Inc, of Temecula, California. FIG. 1 depicts such a conventional over-the-wire balloon catheter 1. The conventional balloon catheter 1 is utilized in an angioplasty procedure as follows. A conventional guidewire 2 is inserted into the patient's artery until the distal end of the guidewire 2 is past a target area (not shown) of the artery (not shown) where there is a buildup of material. The conventional balloon catheter 1 has a lumen 3 running therethrough. The guidewire 2 is inserted into the distal end of the balloon catheter 1 and the balloon catheter 1 is advanced over the guidewire until the balloon section 1a of the balloon catheter 1 is adjacent the buildup of material. The balloon section 1a is then inflated by an inflation means (not show) connected to an inflation port 1b to clear the artery. Finally, the balloon section 1a is deflated, the balloon catheter 1 is pulled back up the guidewire and removed and the guidewire is likewise removed from the patient's artery.
The main concern associated with using balloon catheters is the possibility of balloon failure or rupture, and the resulting biological and radiological toxicity.
Approximately 40% of patients undergoing this procedure is have angiographic evidence of restenosis by 12 months. The mechanism of the restenosis process is not well understood, but both animal and human data suggest that it involves smooth muscle cell migration, proliferation, and neointima formation (6-9). Restenosis after stent implantation occurs at a somewhat lower rate of about 20%. Efforts to prevent restenosis using a variety of pharmacological or mechanical interventions or both have been largely unsuccessful in human and porcine models (10-19).
Although coronary artery blockage is a non-malignant disease, it has been suggested that treatment of the internal vessel walls with ionizing radiation could inhibit cell growth, and delay or even prevent restenosis (24, 36-40). There exists a long and extensive experience with the use of ionizing radiation to treat non-malignant disease such as aneurysmal bone cysts, arteriovenous malformations, arthritis, chondroma, heterotopic bone formation, total lymphoid irradiation (for renal and heart transplantation), and pterygium (reviewed in 28). Although this suggests that ionizing irradiation can be used to treat non-malignant, proliferative disorders, delivering such irradiation while minimizing damage to surrounding tissue has been a problem. And, in the case of balloon catheters, a continuous safety concern has been the rupture of the balloon and release of radioactive material into the bloodstream.
Details on catheters and their use can be found in U.S. Pat. No. 5,059,166, U.S. Pat. No. 5,213,561, U.S. Pat. No. 5,503,613, and PCT International Publication WO 95/19807. The disclosures of these documents in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.